Deflectable renal nerve ablation catheter

ABSTRACT

Medical devices including catheters for renal nerve ablation and/or modulation as well as methods for making and using such devices are disclosed. An example catheter may, have a proximal region and a distal region. The catheter may be configured to shift between a first straightened configuration and a second deflected configuration. The catheter may also include an ablation member coupled to the distal region and a handle coupled to the proximal region. The handle may include an actuation member for shifting the catheter between the first configuration and the second configuration. A lock may be coupled to the handle that maintains the catheter in either the first configuration or the second configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 61/562,200, filed Nov. 21, 2011, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure pertains generally to medical devices. More particularly, the disclosure pertains to deflectable renal nerve modulation and/or ablation catheters.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed for medical use, for example, intravascular use. Some of these devices include guidewires, catheters, and the like. These devices are manufactured by any one of a variety of different manufacturing methods and may be used according to any one of a variety of methods. Of the known medical devices and methods, each has certain advantages and disadvantages. There is an ongoing need to provide alternative medical devices as well as alternative methods for manufacturing and using medical devices.

SUMMARY

Medical devices as well as methods for making and using medical devices are disclosed. An example medical device may include a catheter having a proximal region and a distal region. The catheter may be configured to shift between a first straightened configuration and a second deflected configuration. An ablation member or ablation members may be coupled to the distal region. A handle may be coupled to the proximal region. The handle may include an actuation member for shifting the catheter between the first configuration and the second configuration. A lock may be coupled to the handle for maintaining the catheter in either the first configuration, the second configuration, or at any point between the two configurations.

Another example medical device may take the form of a device for ablating nerves disposed adjacent to a renal blood vessel. The medical device may include a renal nerve ablation catheter having a proximal region and a distal region. A pull wire may be coupled to the catheter. The pull wire may be configured to shift the catheter between a first straightened configuration and a second deflected configuration. An ablation member or ablation members may be coupled to the distal region. A handle may be coupled to the proximal region. The handle may include a carriage coupled to the pull wire and a slider button coupled to the carriage. A lock may be positioned within the handle and disposed adjacent to the catheter. The lock may be configured to maintain the configuration of the catheter.

An example method for ablating renal nerves may include providing a renal nerve ablation catheter. The catheter may include a catheter body having a proximal region and a distal region, a pull wire coupled to the catheter body, an ablation member coupled to the distal region, a handle coupled to the proximal region, and a lock positioned within the handle. The pull wire may be configured to shift the catheter body between a first straightened configuration and a second deflected configuration. The handle may include a carriage coupled to the pull wire and a slider button coupled to the carriage. The lock may be configured to maintain the configuration of the catheter body. The method may also include advancing the ablation catheter through a body lumen to a position adjacent to renal nerves and actuating the slider button. Actuating the slider button may pull the pull wire and shift the catheter body from the first configuration to the second configuration. The method may also include releasing the slider button. Releasing the slider button may cause the lock to maintain the catheter body in the second configuration.

The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the present disclosure and together with the description, serve to explain the principles of the disclosure.

FIG. 1 is a schematic view illustrating an example renal nerve modulation system.

FIG. 2 is a schematic view illustrating the location of the renal nerves relative to the renal artery.

FIG. 3 is a side view of an example catheter in a straightened configuration.

FIG. 4 is an alternative side view of an example catheter in a deflected configuration.

FIG. 5 is a cross-sectional side view of a portion an example medical device.

FIGS. 5A-5B are graphs that schematically illustrate how a locking mechanism with lower friction may provide enhanced tactile feel.

FIG. 6 is a cross-sectional side view of a portion of the example medical device shown in FIG. 5 in a second or “unlocked” configuration.

FIG. 7 is cross-sectional side view of a portion of another example medical device.

FIG. 8 is cross-sectional side view of the example medical device shown in FIG. 7 in a second or “unlocked” configuration.

FIG. 9 is cross-sectional side view of another example medical device.

FIG. 10 is a cross-sectional side view of the example medical device shown in FIG. 9 in a second or “unlocked” configuration.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with one embodiment, it should be understood that such feature, structure, or characteristic may also be used connection with other embodiments whether or not explicitly described unless clearly stated to the contrary.

Certain treatments may require the temporary or permanent interruption or modification of select nerve function. One example treatment is renal nerve ablation which is sometimes used to treat conditions related to hypertension, congestive heart failure, or other conditions. The kidneys produce a sympathetic response to congestive heart failure, which, among other effects, increases the undesired retention of water and/or sodium. Ablating some of the nerves running to the kidneys may reduce or eliminate this sympathetic function, which may provide a corresponding reduction in the associated undesired symptoms.

Many nerves (and nervous tissue such as brain tissue), including renal nerves, run along the walls of or in close proximity to blood vessels and, thus, can be accessed intravascularly through the walls of the blood vessels. In some instances, it may be desirable to ablate perivascular nerves using a radio frequency (RF) electrode. In other instances, the perivascular nerves may be ablated by other means including application of thermal, ultrasonic, laser, microwave, and other related energy sources to the vessel wall.

Renal nerve ablation may require precise control of the catheter during treatment. Because the nerves may be hard to visualize, treatment methods employing such energy sources have tended to apply the energy as a generally circumferential ring to ensure that the nerves are modulated. However, such a treatment may result in thermal injury to the vessel wall near the electrode and other undesirable side effects such as, but not limited to, blood damage, clotting, weakened vessel wall, and/or protein fouling of the electrode. Once the desired tip deflection is achieved, the operator must maintain that position stably during ablation. Afterward, the catheter can be straightened and repositioned for additional ablation, if desired. Catheter control is enhanced by tactile feedback, to help the user apply appropriate force between the catheter and the surrounding tissue. Tactile feedback takes advantage of the user's sense of touch by relaying forces to the user.

Some embodiments of the present disclosure include a medical device for ablating a target tissue within a patient's body. The medical device may take the form of a catheter having a deflectable distal end. The catheter may be configured to ablate a desired body tissue by, for example, applying RF energy. The catheter's handle may include a mechanism for remotely manipulating the distal end of the catheter. Further, the handle may include a locking mechanism that can assist in locking the deflected catheter tip in a desired direction. For example, the handle may include a pivot plate lock mechanism, a roll pin deflection lock mechanism, or a tilt plate deflection lock mechanism. In addition, an actuator such as a slider may be actuated to deflect and lock the distal end of the catheter in the desired direction. These are just examples.

Some catheters may include a convention friction lock handle that may lock a catheter in a deflected configuration by coupling the pull wire to the handle using a simple friction lock. The force the user feels when using this handle in free space is the combination of the internal handle sliding friction (which may be significant to prevent position loss at a maximum deflection) and the force required to deflect the catheter (which is typically a linear function of pull wire displacement).

In addition, the locking mechanisms disclosed herein may also be fabricated to be low friction locking mechanisms such that the forces between the catheter tip and the vessel wall are more easily felt by the clinician than friction forces that may be present in the locking mechanism itself Because of this, the clinician may more easily be able to detect whether or not the catheter tip has engaged the vessel wall. The design of the locking mechanisms that are contemplated (e.g., including those example locking mechanisms disclosed herein) include a structural balance between providing sufficient locking force while still providing lower friction and increase tactile feedback. Such designs may including, among other things, levers, tapered structures, inclined surfaces and/or structures, angled members, or the like that can provide at least some of these features.

The locking mechanisms may also lock the pull wire only when the user is no longer moving an actuator or slider. Because of this, the force the user feels is essentially only the force required to deflect the catheter. In the confined space of an artery, when the deflected catheter makes contact with the vessel wall, it may be much easier for a user to detect vessel contact with the low friction handles and locking mechanisms disclosed herein, for example, because the friction in the conventional handles “mask” the effect of the change in the force versus pull wire displacement slope at a given handle actuation force.

The ablation catheter, in the following sections, may be employed to modulate or ablate renal nerves. The ablation catheter may include a single ablation member or electrode, a plurality of ablation electrodes, expanding basket catheters, etc. It will be understood that this choice is merely exemplary and the catheter may be used in any desired body lumen (including intravascular locations) requiring ablation without departing from the scope of the present disclosure.

While the devices and methods described herein are discussed relative to renal nerve modulation through a blood vessel wall, it is contemplated that the devices and methods may be used in other applications where nerve modulation and/or ablation are desired. The term modulation refers to ablation and other techniques that may alter the function of affected nerves.

For purposes of this disclosure, “proximal” refers to the end closer to the device operator during use, and “distal” refers to the end further from the device operator during use.

FIG. 1 is a schematic view of an illustrative renal nerve modulation system 100 in situ. System 100 may include one or more conductive element(s) 102 providing power to renal ablation system 104 disposed within a sheath 106, the details of which can be better seen in subsequent figures.

A proximal end of conductive element 102 may be connected to a control and power element 108, which supplies the necessary electrical energy to activate the one or more electrodes at or near a distal end of the renal ablation system 104. In some instances, return electrode patches 110 may be supplied on the legs or at another conventional location on the patient's body to complete the circuit. The control and power element 108 may include monitoring elements to monitor parameters such as power, temperature, voltage, amperage, impedance, pulse size and/or shape and other suitable parameters as well as suitable controls for performing the desired procedure. The power element 108 may control a radio frequency (RF) electrode, which may be configured to operate at a frequency of approximately 460 kHz. It is contemplated that any desired frequency in the RF range may be used, for example, from 450-500 kHz. It is, however, contemplated that different types of energy outside the RF spectrum may be used as desired, for example, but not limited to ultrasound, microwave, acoustic, optical, and laser.

FIG. 2 illustrates a portion of the renal anatomy 200 in greater detail. More specifically, the renal anatomy includes renal nerves 202 extending longitudinally along the lengthwise dimension of renal artery 204 and generally within the adventitia of the artery. As will be seen in the figure, the circumferential location of the nerves at any particular axial location may not be readily predicted. Nerves 202 are difficult to visualize in situ and so treatment methods may desirably rely upon ablating multiple sites to ensure nerve modulation

A side view of a portion of renal ablation system 104 is shown in FIGS. 3 and 4. System 104 may include a flexible, elongated catheter 302, which may include a catheter shaft 303 having its proximal end connected to a handle 304 and having a distal tip 312 including an ablation member 314 disposed adjacent to or otherwise coupled therewith. The particular configuration and size of the handle 304 can vary and may include a number of different lengths, sizes, etc., as determined by the particular needs of a given procedure. It should also be appreciated that the catheter handle 304 may also vary in shape based on the comfort of a user handling the renal ablation system 104. In at least some embodiments, the ablation member 314 may be an RF ablation electrode. This is just an example as other ablation members are contemplated. Handle 304 includes a handle housing 310 with a distal end region 306 coupled to the catheter shaft 303 and a proximal end region 308. A deflection wire (not shown in FIGS. 3-4, can be seen in FIGS. 5-10 and may also be referred to as a pull wire) may be disposed within the handle housing 310, may extend along at least portion of (e.g., along the interior, exterior, or both) catheter shaft 303 and be attached at a position adjacent to distal tip 312 (e.g., adjacent to ablation member 314). The deflection wire may also be connected to other structures inside the handle 304, as discussed in more detail below.

Deflection of the catheter tip 312 may be controlled by an active deflection mechanism (also referred to as an actuation mechanism). The active deflection mechanism may be located inside the catheter handle 304; though it should be appreciated that the active deflection mechanism may be located at any other suitable location. For actuation, the catheter handle 304 may also include an actuation member or a slider button 316 and/or a rotating cap 318. The rotating cap 318 may or may not be made so that it independently rotates relative to the handle housing 310. The slider button 316 and the rotating cap 318 may be designed to allow user manipulation of catheter shaft 303, which may analogously shift the position of ablation member 314. For example, sliding the slider button 316 along handle housing 310 may shift catheter shaft 303 between a generally straightened configuration (e.g., as shown in FIG. 3) and a generally deflected configuration (e.g., as shown in FIG. 4). Likewise, rotation of rotating cap 318 may rotate catheter shaft 303. These and other elements may cooperate as part of an actuation mechanism that may be used to rotate and/or deflect the catheter 302.

When the slider button 316 is not being operated, a locking mechanism, examples of which are discussed below, may help maintain the catheter tip 312 in either a straightened, deflected, or partially deflected state. Once the catheter tip is 312 deflected to the desired extent, the user may release the slider button 316. That action automatically activates the locking mechanism to prevent the catheter tip 312 from returning to the original straightened configuration. The mechanical arrangement utilized for the structural features of renal ablation system 104, may help control the forces felt by the user during deflection so that the forces felt by the user are almost entirely those produced by pressure of the catheter tip 312 against the vessel wall and the forces required to deflect the catheter, providing superior tactile feedback to the user. It can be appreciated that the locking mechanism can be utilized, in at least some embodiments, to lock the catheter tip 312 in a straightened configuration, a curved configuration, or any configuration therebetween.

FIGS. 5-10 illustrate some of embodiments contemplated for locking mechanisms that may be adapted to hold the catheter tip 312 in a deflected or partially deflected state. Common features of those embodiments can be discerned before examining particular characteristics of each embodiment. In broad terms, the locking mechanism may include a carriage 502, shown in FIG. 5, and a carriage shaft 503. Carriage shaft 503 may be coupled to the handle housing 310. In some embodiments, the carriage shaft 503 may take the form of a metal rod. Other forms are also contemplated. Carriage 502 is generally carried within handle 304, and is configured to slide distally and proximally within the handle 304 along, for example, the carriage shaft 503. In at least some embodiments, the slider button 316 is also coupled to the carriage 502 so that sliding motion of the slider button 316 along the outside of the handle 304 may result in corresponding motion of the carriage 502.

Carriage 502 may include a cavity 504, extending lengthwise therethrough. A pull wire 506 may be disposed within cavity 504. The proximal end of the pull wire 506 may be connected to carriage 502 at a first point (also referred to as an anchor point 508) as shown in FIGS. 5-10. The distal end of the pull wire 506 may be extended and connected to catheter shaft 303, for example at a position adjacent to distal tip 312. This may include extending pull wire 506 through catheter shaft 303, along an exterior surface of catheter shaft 303, both, etc. to a position where pull wire 506 is coupled or otherwise attached to catheter shaft 303 (e.g., at or near distal tip 312). Accordingly, movement of the carriage 502 (e.g., by actuating the slider button 316) results in movement of the pull wire 506 and deflection (and/or straightening, depending on direction) of the catheter shaft 303. The pull wire 506, optionally, may be disposed within a sleeve or housing 510.

One embodiment of the locking mechanism that may be configured to hold catheter shaft 303 in a deflected or partially deflected configuration is a pivot plate lock mechanism 500, shown in FIGS. 5 and 6. In the illustrated embodiment, the pivot plate lock mechanism 500 may include an actuation member 511 that may take the form of a switch handle or toggle that may extend upward through the surface of handle 304 and be accessible to a user. Actuation member 511 may be pivotably mounted on carriage 502 for rotation proximally and distally around a pivot joint 512. In some embodiments, the actuation member 511 (e.g., the portion extending through the handle 304) may be positioned alongside or adjacent to slider button 316. In other embodiments, the actuation member 511 may be a structural feature incorporated into the slider button 316.

Carriage 502 includes a channel 514 formed therein. A pivot plate 516 may be disposed in channel 514 that is coupled to or otherwise is configured to ride along carriage shaft 503. The channel 514 having the pivot plate 516 is designed so that the carriage shaft 503 can slide through the pivot plate 516 without binding when pivot plate 516 stands substantially perpendicular relative to the carriage shaft 503 (e.g., which allows analogous movement of the catheter shaft 303) yet restrict movement of the carriage 502 along the carriage shaft 503 when pivot plate 516 is “pivoted”.

One or more springs (or biasing springs) 518 may be connected to, for example, the edge of pivot plate 516 and a transverse side of channel 514, as shown in FIG. 5. For example, the spring 518 may connect to the upper edge of the pivot plate 516 or some other location. The biasing spring 518 may take the form of a coil spring or any other suitable structure. When mechanism 500 is in a first or “locked” configuration (e.g., as shown in FIG. 5), biasing spring 518 may be configured to exert a force on pivot plate 516 so as to “pivot” the pivot plate 516, which may orient pivot plate 516 at an angle relative to the carriage shaft 503 and wedge it against the carriage shaft 503. The tilted or pivoted position of the pivot plate 516 restricts the movement of the carriage 502 distally (e.g., toward the right on the FIG. 5) along the carriage shaft 503.

To deflect the catheter tip 312, the user pulls the slider button 316 proximally (to the left in FIG. 5). In doing so, the carriage 502 slides proximally along the carriage shaft 503. The orientation of the pivot plate 516 allows carriage 502 to slide along the carriage shaft 503 in this direction (e.g., the proximal direction). As the carriage 502 slides along the carriage shaft 503, the tension forces in the pull wire 506 increase as illustrated with the force arrow positioned adjacent to the pull wire 506 (pointed to the right). The tension forces are balanced by the friction forces at the contact points between the pivot plate 516 and the carriage shaft 503 (depicted with arrows pointed to the left). Because the friction forces balance the tension forces, the carriage is effectively “locked” from motion to the right. However, the carriage 502 may still be permitted to slide proximally. Accordingly, the lock mechanism 500 may be described as a “one-way” lock that allows for proximal movement of the carriage 502 (and corresponding deflection of the catheter shaft 303) while substantially preventing distal movement of the carriage (and corresponding straightening of the catheter shaft 303) when in the “locked” configuration.

To “unlock” the lock mechanism 500, the user may tilt or pivot the toggle 511. When doing so, a leg portion 513 of toggle 511 (e.g., a bottom portion or projection of toggle 511 disposed adjacent to pivot joint 512) may exert a force onto pivot plate 516. The force from the leg portion 513 on the pivot plate 516 may overcome the bias of spring 518 and allow pivot plate 516 to “pivot” to a more upright or perpendicular position relative to the carriage shaft 503. With pivot plate 516 in an upright position, carriage 502 can slide relative to the carriage shaft 503 in either direction. This “unlocked” configuration is illustrated in FIG. 6.

Returning the toggle 511 to a more upright configuration removes or reduces the force exerted by the leg portion 513 on the pivot plate 516 and allows the spring 518 to return the pivot plate 516 to the pivoted orientation (e.g., where the pivot plate 516 can wedge against the carriage shaft 503), again “locking” the carriage 502 (e.g., preventing the carriage 502 from moving to the right or distally). The locking may be considered “automatic” and occur almost instantly upon release of the toggle 511. Thus, in use the proximal movement of carriage 502 pulls the pull wire 506 (fixed to anchor point 508) in the same direction. As the pull wire 506 moves proximally with respect to shaft 303, the catheter tip 312 deflects (e.g., as shown in FIG. 4). To return the catheter tip 312 to an undeflected configuration, the user can again actuate the actuation member 511 (e.g., to the “unlocked” configuration as shown in FIG. 6) and urge slider button 316 distally, which moves the pull wire 506 distally with respect to shaft.

The locking mechanism 500 may impose very low friction on the system, allowing the user to feel the forces between the catheter tip 312 and the vessel wall, providing excellent tactile feedback. For example, the force required to deflect the catheter tip 312 (which itself may increase in, for example, a linear manner as the catheter tip 312 is further deflected) may be considerably lower than the force required to deflect a catheter tip when using a friction lock handle (which also may increase in, for example, a linear manner as the catheter tip is further deflected). This is shown schematically in FIG. 5A. Upon contacting the vessel wall, an abrupt change in force (e.g., tending to resist further deflection) may occur. Because the deflection forces may be much lower when using the locking mechanisms disclosed herein, the user may be able to readily detect this abrupt change in force whereas in convention systems the force may be “masked” by the higher deflection forces and may not be as readily detected by the user. In other words, because deflecting the catheter tip 312 may require less force than convention friction based mechanisms, the relative percent change in the force that occurs when the catheter tip 312 contacts the vessel wall may be more easily perceived by the user.

The relative levels of force may be varied. For example, the force required to deflect a catheter shaft (and overcome the friction of the lock) in a conventional system with a friction lock may be on the order of about 1-5 pounds, or about 2-3 pounds, or about 2.2 pounds. In contrast, the forces required to deflect the catheter tip may be less than about 1 pound, or about 0.1 to 0.5 pounds, or about 0.2 pounds. These are just examples. In at least some embodiments, the locking mechanism 500 may reduce the amount of force needed to deflect the catheter tip 312 by about 40-95%, or about 50-95%, or about 60-95%, or about 70-95%, or about 80-95%, or about 85-90%. These are just examples.

In addition, FIG. 5B shows the instantaneous slope of the handle actuation force versus pull wire displacement (relative to the applied force at that point) for handles with either convention friction-based locking mechanism versus handles with low friction locking mechanism like those disclosed herein. Again, the overall or relative change in force is greater and more easily detectable by the user when using a lower friction locking mechanism such as any of those disclosed herein.

When the desired amount of deflection is achieved, the user can release the actuation mechanism 511, returning pivot plate 516 to its wedged position. In this configuration, the actuation mechanism 511 resists forces applied by the blood vessel walls or by the catheter elastic recovery forces, retaining catheter tip 312 in its deflected state. Thus, the movement of the catheter tip 312 is effectively locked in the deflected state. Repeated iterations of this movement pattern increases the deflection of the catheter tip 312 by moving the pull wire 506 proximally with respect to the catheter shaft 303. This mechanism may be similar to the ratcheting action in a caulking gun or similar structure.

It should be noted that while the locking mechanism 500 is generally shown as being configured to lock or otherwise prevent the catheter tip 312 from straightening when in a curved configuration, the locking mechanism 500 can also be configured to essentially lock the catheter tip 312 in either direction.

An alternative embodiment of the active deflection mechanism is a roll pin automatic deflection lock mechanism 700, shown in FIGS. 7 and 8. This mechanism may include a lever 702 pivotably mounted inside the carriage 502 and extending into a sliding button 704 as shown in FIGS. 7-8. A roll pin 706 may be movably located in a downwardly inclined ramp 708 formed in the carriage 502. A stop member 709 may also be disposed along ramp 708 and a spring 710 may be coupled to the stop member 709. When the deflection lock mechanism 700 is in the “locked” configuration as shown in FIG. 7, the position of the lever 702 may be adjacent to the roll pin 706, and spring 710 may urge the stop member 709 so that the roll pin 706 wedges against the carriage shaft 503.

Much like the lock mechanism 500, lock mechanism 700 may also be described as being a “one-way” lock that allows the carriage 502 to slide proximally along the carriage shaft 503 while substantially preventing the carriage 502 from sliding distally when “locked”. For example, the tension forces in the pull wire 506 are balanced by the friction forces between the roll pin 706 and the carriage shaft 503.

To shift the lock mechanism 700 to the “unlocked” configuration, the user may distally slide button 704 as shown in FIG. 8. This rotates the lever 702 into a slightly more angled orientation so that the lever 702 exerts a distal force on the roll pin 706, shifting the roll pin 706 to the right. This may also shift the stop 709 and compress the spring 710. When the roll pin 706 is shifted, the carriage 502 may move freely in the distal direction with respect to the carriage shaft 503. Removing the distal force from the slider button 704 allows the lever 702 to “automatically” shift back to its more upright orientation (e.g., as shown in FIG. 7) and wedge the roll pin 706 back into the carriage shaft 503.

The leverage provided by lever 702 may advantageously help to reduce the actuation force and to make operation smooth and reliable. When designing the actuation mechanism 700, the lever arm LA₁ defined between a contact point between a top portion of the lever 702 and the bottom contact point or fulcrum may be designed to be larger than the lever arm LA₂ defined between the roll pin 706 (e.g., at the point of contact with between the lever 702 and the roll pin 706) and the fulcrum. For example, the length of LA₁ may be about 2-10 times larger than LA₂, or the length of LA₁ may be about 3-9 times larger than LA₂, or the length of LA₁ may be about 4-6 times larger than LA₂, or the length of LA₁ may be about 4-5 times larger than LA₂. In one example embodiment, the length of LA₁ may be about 0.433 inches and the length of LA₂ may be about 0.110 inches. These are just examples and other lengths and/or ratios of relative lengths are contemplated for LA₁ and LA₂.

In addition to variations in the lengths of the lever arms LA₁/LA₂, other variations are also contemplated including variations in the spring stiffness of spring 710, the incline angle or configuration of ramp 708, as well as other variations. Such variations may further reduce friction in the lock mechanism 700 and, for example, may further enhance the tactile feel.

In a further alternative embodiment, the active deflection mechanism is a tilt plate deflection lock mechanism 900 shown in FIG. 9 and FIG. 10. This mechanism 900 locks the carriage 502 in position when at rest, releasing that lock when the user depresses a slider. Here, the slider button 316 is a cap 902 that overlies carriage 502 and is pivotably attached to the carriage at a pivot point 904. Cap 902 can include protrusions designed for user handling and comfort as desired. A notch 905 may be formed in the lower surface of cap 902, the notch 905 being formed in the surface of cap 902 with an inclined slope extending toward the distal end of cap 902. Locking action is provided in this embodiment by a tilt plate 906, a generally rectangular element carried in a channel 908 in a distal portion of carriage 502. The lower edge of tilt plate 906 may be rotatably carried in a slot 910 or other convenient mounting location at the bottom of channel 908. An aperture or other convenient structure in tilt plate 906 allows it to fit over the carriage shaft 503, and it is secured in place by attachment to a compression spring 912 mounted at the upper end of channel 908, for example above the location where the carriage shaft 503 passes through the carriage body. Spring 912 is sized so that in the spring's uncompressed state, tilt plate 906 stands tilted proximally, with its upper end extending into the initial portion of notch 905. In that position, the tilt plate 906 engages the carriage shaft 503 so that the carriage 502 is locked in position.

To increase or decrease the deflection of the catheter tip 312, the user first unlocks the carriage by depressing the cap 902, as shown in FIG. 10. That action presses the inclined surface of notch 905 against the upper edge of tilt plate 906, compressing spring 912 and rotating tilt plate 906 into a generally upright position. There, tilt plate 906 disengages from the carriage shaft 503, allowing carriage 502 to move either distally or proximally. To increase the deflection of catheter tip 312, the user moves carriage 502 proximally, which moves the pull wire 506 with respect to shaft 303 and deflects catheter tip 312 as shown in FIG. 4. Conversely, moving carriage 502 distally decreases the deflection of catheter tip 312, as discussed above.

Although the embodiments described above have been set out in connection with a renal nerve ablation catheter, those of skill in the art will understand that the principles set out there can be applied to any catheter or endoscopic device where it is deemed advantageous to deflect the tip of the device. Conversely, constructional details, including manufacturing techniques and materials, are well within the understanding of those of skill in the art and have not been set out in any detail here. These and other modifications and variations are well within the scope of the present disclosure and can be envisioned and implemented by those of skill in the art.

Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. It is intended that the specification and examples be considered as exemplary only, and departure in form and detail may be made without departing from the scope and spirit of the present disclosure as described in the following claims. 

What is claimed is:
 1. A medical device, comprising: a catheter having a proximal region and a distal region; wherein the catheter is configured to shift between a first straightened configuration and a second deflected configuration; an ablation member coupled to the distal region; a handle coupled to the proximal region; wherein the handle includes an actuation member for shifting the catheter between the first configuration and the second configuration; and a lock coupled to the handle for maintaining the catheter in either the first configuration or the second configuration.
 2. The medical device of claim 1, wherein the actuation member includes a slider that is configured to slide along an exterior surface of the handle.
 3. The medical device of claim 1, wherein the lock maintains the catheter in the first configuration.
 4. The medical device of claim 1, wherein the lock maintains the catheter in the second configuration.
 5. The medical device of claim 1, wherein a pull wire is coupled to the actuation member.
 6. The medical device of claim 5, wherein the lock includes a carriage attached to the pull wire, a pivot plate disposed within a channel formed in the carriage and disposed about a carriage shaft, and a biasing spring coupled to the pivot plate.
 7. The medical device of claim 6, wherein prior to actuating the actuation member the pivot plate is engaged with the carriage shaft and distal movement of the carriage relative to the carriage shaft is prevented, and wherein pivoting the pivot plate allows the carriage to slide distally along the carriage shaft.
 8. The medical device of claim 5, wherein the lock includes a carriage attached to the pull wire, a roll pin disposed within a channel formed in the carriage and positioned adjacent to a carriage shaft, and a biasing spring coupled to the roll pin.
 9. The medical device of claim 8, wherein prior to actuating the actuation member the roll pin is engaged with the carriage shaft and distal movement of the carriage relative to the carriage shaft is prevented, and wherein actuating the actuation member causes the roll pin to roll out of engagement with the carriage shaft so that the carriage can move distally relative to the carriage shaft.
 10. The medical device of claim 5, wherein the lock includes a carriage attached to the pull wire, a tilt plate disposed within a channel formed in the carriage and positioned about a carriage shaft, and a biasing spring coupled to the tilt plate.
 11. The medical device of claim 10, wherein prior to actuating the actuation member the tilt plate is engaged with the carriage shaft so that the carriage is locked relative to the carriage shaft, and wherein actuating the actuation member tilts the tilt plate so that the carriage can move relative to the carriage shaft.
 12. The medical device of claim 11, wherein the actuation member includes a depressible button, and wherein actuating the actuating member includes depressing the depressible button.
 13. A medical device for ablating nerves disposed adjacent to a renal blood vessel, the medical device comprising: a renal nerve ablation catheter having a proximal region and a distal region; a pull wire coupled to the catheter, the pull wire being configured to shift the catheter between a first straightened configuration and a second deflected configuration; an ablation member coupled to the distal region; a handle coupled to the proximal region; wherein the handle includes a carriage coupled to the pull wire and a slider button coupled to the carriage; and a lock positioned within the handle, the lock being configured to maintain the configuration of the catheter.
 14. The medical device of claim 13, wherein the lock includes a pivot plate disposed within a channel formed in the carriage and positioned about a carriage shaft.
 15. The medical device of claim 14, wherein the lock includes an actuation member that is configured to pivot the pivot plate so that the carriage can move relative to the carriage shaft.
 16. The medical device of claim 13, wherein the lock includes a roll pin disposed within a channel formed in the carriage.
 17. The medical device of claim 16, wherein sliding the slider button along the handle causes the roll pin to roll out of engagement with a carriage shaft so that the carriage can move relative to the carriage shaft.
 18. The medical device of claim 13, wherein the lock includes tilt plate disposed within a channel formed in the carriage and a biasing spring coupled to the tilt plate.
 19. The medical device of claim 13, wherein the lock further comprises a biasing spring.
 20. A method for ablating renal nerves, the method comprising: providing a renal nerve ablation catheter, the catheter comprising: a catheter body having a proximal region and a distal region, a pull wire coupled to the catheter body, the pull wire being configured to shift the catheter body between a first straightened configuration and a second deflected configuration, an ablation member coupled to the distal region, a handle coupled to the proximal region, wherein the handle includes a carriage coupled to the pull wire and a slider button coupled to the carriage, and a lock positioned within the handle, the lock being configured to maintain the configuration of the catheter body; advancing the ablation catheter through a body lumen to a position adjacent to a renal nerve; actuating the slider button, wherein actuating the slider button pulls the pull wire and shifts the catheter body from the first configuration to the second configuration; and releasing the slider button, wherein releasing the slider button causes the lock to maintain the catheter body in the second configuration. 